The greatly expanded San Francisco Museum of Modern Art, which will have twice as much gallery space and open up to the surrounding South of Market streets and alleys when it reopens in 2016, will have two new outdoor terraces: one on the seventh, or top floor, facing east with expansive views, and a third-floor sculpture terrace flanked by what's billed as the city's largest public "living wall" of native plants. It will be 150 long by 35 feet tall.

The building will also include a flexible new tall-ceiling "white box" space with theatrical lighting and sound on the fourth floor, designed for live performances and other presentations.

Those are some of the new details SFMOMA announced Thursday as it fleshed out its plans for the 235,000-square-foot expansion designed by the hot Norwegian architectural firm Snøhetta and its lead designer, Craig Dykers.

With a new 200-foot-tall wing rising behind the bold 1994 red-brick and zebra-striped granite building designed by Mario Botta, the museum will double in size to 470,000 square feet, 130,000 of it devoted to galleries. So far, SFMOMA has raised $437 million of its $555 million capital campaign goal. It will pay not just for the construction and operation of the big building, but for expanding the staff as well.

"We're projecting about 100 new staff members. We're at 250 now," said SFMOMA Director Neal Benezra, who expects construction to begin as planned this summer. The museum closes after a free public day June 2, and is scheduled to reopen in early 2016.

Many of the works in the permanent collection will be stored at a South Bay facility. It will have conservation facilities, and a test gallery will be built there to explore ways of lighting the art in the new galleries.

"You just don't order light fixtures out of a catalog," Benezra said. "There has been a dramatic change in gallery lighting in newer museums in recent years. I believe the Whitney may also be converting to LED lighting. That's one of the things we really want to study in the test gallery we're building. The architects have proposed a particular ceiling configuration that would provide ambient lighting as well as object lighting."

The museum plans to plop sculptor Richard Serra's giant "Sequence" - curling ribbons of leaning, rusted steel that stand 13 feet high - in a big new ground-floor gallery when the building reopens. It will be visible from Howard Street and from a walkway connecting Howard to Minna Street through 25-foot-tall glass walls.

The public can enter that gallery, as well as lobby of the Botta building, for free. One of the signatures of the Botta structure - the atrium's wide three-story staircase - is being demolished to open the way from Third Street to the foyer of the addition and blur the distinction between the older structure and the new one.

"We've turned from the external character of the building and its site to how the museum is going to work," Benezra said. "That's our focus now: How we can make the most seamless connections between the gallery experiences of the Botta building and the new spaces."